Disorders of the shoulder

Question 1

What is the common type of shoulder dislocation and why?

Answer 1

Anterior
- The glenoid fossa is shallow
- Although the joint is strengthened on its
superior, anterior and posterior aspects, it is weak at its inferior aspect

Question 2

What is a subcoracoid location shoulder dislocation?

Answer 2

The head of the humerus dislocates anteroinferiorly, but then displaces in an anterior direction (subcoracoid location = 60% of cases) due to the pull of the muscles
and disruption of the anterior capsule and ligaments.

Question 3

What is a subglenoid location shoulder dislocation?

Answer 3

The head of the humerus comes to lie antero-inferior to the glenoid (subglenoid location = 30% of cases)
- Hand behind head, force of arm posteriorly

Question 4

How does the arm present in an anterior shoulder dislocation?

Answer 4

The arm is held in a position of external rotation and slight abduction
- Direct blow to posterior shoulder

Question 5

What is a Bankart lesion or labral tear?

Answer 5

The force of the humeral head popping out of the socket often causes part of
the glenoid labrum to be torn off. Sometimes a small piece of bone can be torn off with the labrum.

Question 6

What is a Hill-Sachs lesion?

Answer 6

When the humeral head is dislocated anteriorly, the tone of the infraspinatus
and teres minor muscles means that the posterior aspect of the humeral head
becomes jammed against the anterior lip of the glenoid fossa. This can cause a dent (indentation fracture) in the posterolateral
humeral head.

Question 7

What is significant about a Hill-Sachs lesion?

Answer 7

It increases the risk of secondary osteoarthritis in the shoulder joint

Question 8

How can posterior shoulder dislocations occur?

Answer 8

They tend to occur when there are violent muscle contractions due to an epileptic
seizure, electrocution or a lightning strike; when there is a blow to the anterior
shoulder; or when the arm is flexed across the body and pushed posteriorly.

Question 9

How does the arm present in a posterior dislocation?

Answer 9

Internally rotates and adducted. Flattening/squaring of the shoulder with a prominent coracoid process. The arm cannot be externally rotated into the anatomical position.

Question 10

How can a posterior shoulder dislocation be spotted on an X-ray?

Answer 10

A posterior dislocation of the shoulder can easily be missed on an X-ray as it looks ‘in joint’. However, because the arm is internally-rotated, the projection of the humeral head onto the X-ray film changes to a more rounded shape – the ‘light bulb’ sign. The glenohumeral distance is also increased.

Question 11

What injuries are commonly associated with posterior dislocations?

Answer 11

Fractures, rotator cuff tears and Hill-Sachs lesions

Question 12

How might an inferior shoulder dislocation occur?

Answer 12

After inferior dislocation, the head of the humerus sits inferior to the glenoid. The mechanism is forceful traction on the arm when it is fully extended over the head, as may occur when grasping an object above the head to break a fall i.e. a hyperabduction injury.

Question 13

What injuries are associated with posterior shoulder dislocations?

Answer 13

Damage to nerves, rotator cuff tears and injury to blood vessels.

Question 14

What is the most common complication of shoulder dislocation in any direction?

Answer 14

Recurrent dislocation due to damage to the stabilising tissues surrounding the shoulder (glenoid labrum, capsule, ligaments etc.). The chance of further dislocation can be estimated at 60% but depends on age and activity level. As we age, our tissues lose elasticity, so the
risk of recurrent dislocation is approximately 90% in 20-year-olds, falling to only 10% in
40-year-olds. Each dislocation results in further damage to the humeral head and glenoid, therefore it is unsurprising that the risk of osteoarthritis increases with the number of dislocations.

Question 15

Which artery can be damaged in a shoulder dislocation?

Answer 15

Damage to the axillary artery occurs in 1–2% of shoulder dislocations, more commonly in the older age group as their blood vessels are less elastic. The patient may have a haematoma, absent pulses and/or a cool limb.

Question 16

Which nerve can be damaged in a shoulder dislocation?

Answer 16

The axillary nerve wraps around the neck of the humerus, and supplies the deltoid muscle and the skin overlying the insertion of deltoid. This is known as the regimental badge area as it corresponds with where a shoulder badge
would be worn on the sleeve of a jacket. Most people with axillary nerve damage recover fully, as the symptoms resolve when the shoulder is reduced (i.e. put back in position). Less commonly, dislocation of the shoulder may damage the cords of the brachial plexus or musculocutaneous nerve.

Question 17

Why might a fracture occur in a shoulder dislocation?

Answer 17

When there is a traumatic mechanism of injury, first-time dislocation, or the person is aged over 40

Question 18

What are the commonly affected bones if a shoulder dislocation results in a fracture?

Answer 18

Commonly affected bones include the head or greater tubercle of the humerus, the clavicle and the acromion.

Question 19

Where do most clavicle fractures occur?

Answer 19

In the middle third of the clavicle

Question 20

How do most clavicle fractures occur?

Answer 20

Falls onto the affected shoulder or onto the outstretched hand

Question 21

How are clavicle fractures treated?

Answer 21

Most clavicle fractures are treated conservatively (i.e. without surgery), using a sling

Question 22

When might a fractures clavicle need surgical fixation?

Answer 22

• Complete displacement (so the bone ends are not in apposition and cannot unite)
• Severe displacement causing tenting of the skin, with the risk of puncture
• Open fractures (fracture associated with a break in the integrity of skin)
• Neurovascular compromise
• Fractures with interposed muscle
• Floating shoulder: clavicle fracture with ipsilateral fracture of glenoid neck

Question 23

Which nerves can get damaged in a clavicle fracture?

Answer 23

The suprascapular nerve may be damaged by the elevation of the medial part of the fracture. The supraclavicular nerves (C3,4) may also be damaged resulting in paraesthesia over the upper chest anteriorly.

Question 24

What is a rotator cuff tear?

Answer 24

A tear of one or more of the tendons of the four rotator cuff muscles of the shoulder (supraspinatus, infraspinatus, subscapularis and teres minor)

Question 25

Which functions are compromised with a rotator cuff tear?

Answer 25

The rotator cuff is responsible for stabilising the glenohumeral joint, abducting, externally rotating and internally rotating the humerus. When the rotator cuff tendons become torn, these functions are compromised.

Question 26

Which tendon is most often torn in a rotator cuff tear?

Answer 26

he tendons of the rotator cuff are torn much more frequently than the muscles and, of these, the supraspinatus tendon is the most frequently affected where it passes beneath the coracoacromial arch, tearing at the site of its insertion into the greater tubercle of the humerus.

Question 27

How do most rotator cuff tears occur?

Answer 27

Most rotator cuff tears are chronic, resulting from extended use in combination with other factors such as poor biomechanics or muscular imbalance. The most common cause is age-related degeneration. With age, the blood supply to the rotator cuff tendons decreases, impairing the body's ability to repair minor injuries. The principal theory is a degenerative-microtrauma model, which supposes that age-related tendon degeneration, compounded by chronic microtrauma, results in partial tendon tears that then develop into full rotator cuff tears. Inflammatory cells are recruited and oxidative stress leads to tenocyte (tendon cell) apoptosis, leading to further degeneration, thus a 'vicious circle' is created.

Question 28

What type of activity is a risk factor for rotator cuff tears?

Answer 28

Recurrent lifting and repetitive overhead activity are also risk factors (e.g. carpenters, painters), as are sports that involve repeated overhead motion (e.g. swimming, volleyball, tennis, weightlifting). As you would expect, rotator cuff tears are more common in the shoulder of the dominant arm, but a tear in one shoulder signals an increased risk of a tear in the opposite shoulder.

Question 29

What is the most common presentation clinically of rotator cuff tears?

Answer 29

Anterolateral shoulder pain, often radiating down the arm

Question 30

What is impingement syndrome?

Answer 30

Impingement syndrome occurs when the supraspinatus tendon impinges (rubs or catches) on the coraco-acromial arch, leading to irritation and inflammation.

Question 31

How is impingement of the supraspinatus caused?

Answer 31

The space between the head of the humerus and the coracoacromial arch is relatively small (1 - 1.5cm). Impingement may be caused by anything that narrows this space further e.g. thickening of the coracoacromial ligament, inflammation of the supraspinatus tendon, subacromial osteophytes (in osteoarthritis).

Question 32

What causes the pain in impingement syndrome, and what worsens it?

Answer 32

When the shoulder is abducted or flexed, the space becomes narrowed further, resulting in symptoms of pain, weakness and reduced range of motion. The pain is often worsened by shoulder overhead movement and may also occur at night, especially if the patient is lying on the affected shoulder.

Question 33

What is the pain onset it impingement syndrome?

Answer 33

The onset of the pain may be acute if it is due to an injury, or may be insidious (gradually increasing) if it is due to a gradual process such as osteophyte formation. The pain is described as dull rather than sharp, and lingers for long periods of a time, making it hard to fall asleep at night. Other symptoms can include a grinding or popping sensation during movement of the shoulder.

Question 34

What is the most common form of impingement syndrome?

Answer 34

The most common form is impingement of supraspinatus tendon under the acromion during abduction of the shoulder. This creates a ‘painful arc' between 60 and 120 degrees of abduction (below 60°and above 120°, patients experience significantly less, or no, pain). Patients often report pain on reaching upwards to brush their hair or to lift a food can from an overhead shelf.

Question 35

How does calcific supraspinatus tendinopathy present?

Answer 35

It can present with acute or chronic pain, often aggravated by abducting or flexing the arm above the level of the shoulder, or by lying on the shoulder. Mechanical symptoms may also occur due to the physical presence of a large deposit, leading to stiffness, a snapping sensation, catching, or reduced range of movement of the shoulder.

Question 36

How does calcific tendinopathy occur?

Answer 36

Calcific tendinopathy is believed to be multifactorial. One theory is that regional hypoxia leads to tenocytes being transformed into chondrocytes and laying down cartilage in the tendon. Calcium deposits are then formed through a process resembling endochondral ossification. Another theory involves ectopic bone formation from metaplasia of mesenchymal stem cells normally present in tendons into osteogenic cells.

Question 37

When does calcific tendinopathy cause the most pain?

Answer 37

They are crystalline in their 'resting phase'. However, they are eventually reabsorbed by phagocytes, and it is during this reabsorption stage that they tend to cause the most pain.

Question 38

What is adhesive capsulitis?

Answer 38

Adhesive capsulitis, typically referred to as 'frozen shoulder' is a painful and disabling disorder in which the capsule of the glenohumeral joint becomes inflamed and stiff, greatly restricting movement and causing chronic pain. The pain is usually constant, worse at night and exacerbated by movement and cold weather.

Question 39

What are the risk factors for adhesive capsulitis?

Answer 39

* Female gender * Epilepsy with tonic seizures (i.e. sudden muscle contractions) * Diabetes mellitus (the theory is that glucose molecules bond to the capsular collagen) * Trauma to the shoulder * Connective tissue disease * Thyroid disease (hypo and hyperthyroidism) * Cardiovascular disease * Chronic lung disease * Breast cancer * Polymyalgia rheumatica (an inflammatory condition causing muscle pain and weakness) * Parkinson's disease * Long periods of inactivity (from injury, stroke or illness) can precipitate frozen shoulder, and it can also occur alongside other shoulder problems e.g. calcific tendinopathy or rotator cuff tear.

Question 40

How is adhesive capsulitis treated?

Answer 40

Treatment usually involves physiotherapy, analgesia and anti- inflammatory medication. Patients sometimes undergo manipulation under anaesthesia, which breaks up the adhesions and scar tissue in the joint to help restore range of motion. Intense post-operative physiotherapy then helps to maintain the movement that has been gained.

Question 41

What joint of the shoulder does OA mainly affect?